1. Field of the Invention
The present invention relates to a pocket transceiver, for example, a wireless telephone that is small enough to be put into a pocket and operating at a low power level. The transceiver can be connected to an adapter so that its output power is amplified and transmitted, through an external antenna.
2. Description of the Prior Art
FIG. 1 is a circuit diagram showing a prior art portable radio transceiver disclosed, for example, in U.S. Pat. No. 4,636,741. Referring to the figure, reference numeral 1 denotes a transmitting-receiving unit including a microprocessor, 2 denotes a keyboard, 3 denotes a display, 4 denotes a microphone, 5 denotes a speaker, 7 denotes a battery, and 31 denotes a power control, which is composed of a logarithmic amplifier 36, a detector 37, and a power control driver 38. Reference numeral 32 denotes a power amplifier including stages 39 and 40 connected in series. Reference numeral 33 denotes a transmitter filter, 34 denotes a receiver filter, 35 denotes an antenna, 36 denotes a circulator, 41 denotes a power-control switching circuit made up of an inverting gate, 48 denotes a data bus for the microprocessor, 8 denotes an interface between a transceiver 51 and a vehicular adapter 52, 10 denotes a vehicular battery of a vehicle, 9 denotes a battery charger for charging the battery 7, 11 denotes a regulator for generating a reference voltage V.sub.R to be supplied to a power control 12, 12 denotes the power control similar to the power control 31 in the transceiver 51, 13 denotes a power amplifier similar to the power amplifier 32 in the transceiver 51, and 15 denotes a filter similar to the transmitter filter 33 in the transceiver 51, and 17 denotes an external antenna.
The operation of the above structure is described below. When the vehicular adapter 52 is separated at the interface 8, the transceiver 51 operates on the battery 7, and the antenna 35. The transmitter output, in this case, is controlled and set to any of eight levels, from level 1 to level 8, by the microprocessor of the transmitting-receiving unit 1 controlling the power control driver 38, which, in turn, controls the gain of the power amplifier 32.
When the vehicular adapter 52 is connected at the interface 8, the battery 7 is charged by the battery charger 9 through contacts 44a, 44b.
The switching circuit 41 detects through contacts 42a, 42b that a connection is established at the interface 8 and thereupon requests the microprocessor to select another program. Further, the transmitter filter 33 is disconnected from the internal antenna 35 and connected to the power amplifier 13 through contacts 46a, 46b, and the receiver filter 34 is disconnected from the antenna 35 and connected to the external antenna 17 through contacts 47a, 47b. At this time, the output of the power amplifier 32 is set to a predetermined level by the microprocessor, and the power control 12 and the power amplifier 13 on the side of the vehicular adapter 52 generate a desired power level according to the aforesaid predetermined level and supply the power to the filter 15 and the external antenna 17. Since the data bus 48 for the microprocessor is connected to the power control 12 through contacts 45a, 45b, the power control 12 is enabled, in response to, for example, a predetermined message received from the microprocessor, to control the power amplifier 13 to output power in the range from level 1 to level 8.
With the prior art portable transceiver constructed as described above, the portable transceiver has had a large transmitter output, and hence it has required a large capacity of the battery 7. Thus, there has been a problem with the prior art because it is large in size and heavy in weight. In addition, the internal antenna has been of a .lambda./4 rod type or the like and hence its size has also been large.